Seminars
Seminars occur on Wednesdays from 12:00-1:00 PM Pacific in ISB 130 with a hybrid option over Zoom unless otherwise posted. To join the mailing list, please contact Prof. Ehsan Khatami at ehsan.khatami@sjsu.edu with the words "Seminars and Events" included in the subject heading.
Upcoming
Light with a twist: an introduction to twisted light with orbital angular momentum
Mark Siemens, University of Denver
Wednesday, 3/26/2025, 12:00-1:00pm Pacific
Abstract: We normally think of light as traveling straight between points in space, but beams
of light can rotate as they travel. In the simplest rotating beams, the electromagnetic
fields of circularly polarized light rotate with propagation and this “spin angular
momentum” has been well understood for more than 100 years. But less than 30 years
ago, the “orbital angular momentum” form of rotation was discovered that leads to
a “vortex” beam with a helical phase. These vortex beams have many applications, including
control of tiny micromachines, star rotation measurement, super-resolution imaging,
and high-bandwidth communication. Conventional methods for generating and measuring
twisted light involved either expensive and fixed-wavelength optics or computer-controlled
electro-optics such as a spatial light modulator. In this talk, I will 1.) provide
a tutorial explaining the basic concepts of twisted light, 2.) discuss very simple
methods for generating and measuring the orbital angular momentum of light, and 3.)
highlight some of our recent research with twisted light.
Bio: Dr. Mark Siemens is a Professor in the Department of Physics and Astronomy at the University of Denver (DU). His research group controls the spatial and temporal shape of lasers to probe and control basic excitations and transport in nanostructures. He is the faculty advisor for DU’s Society of Physics Students, which is locally and nationally recognized for their physics outreach.
